I’m no expert but all those questions are pretty basic and I can help.
Why buy this projector bracket? So you can install proper projectors with a cutoff line. Lou has a bracket for an H1 mini projector and a bracket for the larger, more expensive D2S projector. You would bake the lights at proper temp to soften the adhesive/silicone and then pull the lenses off to gain access to remove the factory bracket and replace with Lou’s part. Then install the projector and reseal the lenses. After that you would need to buy an HID kit which should include a bulb and ballast at a minimum, some kits even have a relay harness although I’ve never used replays in any of my cars and never had issues after 15+ years.
As far as the lenses go, removing the yellowing and oxidation on the outside of the lens is the easy part. Toyota lenses are a very soft plastic and very easy to sand and polish to a high gloss, then either clear coat them with a 2K clear and/or install paint protection film to prevent the lights from quickly yellowing and becoming dull again. If you skip this step (clearcoat or paint protection film, aka “clearbra”), be ready to repeat the sanding or polishing process at least once a year or sooner because they will yellow again since the oem clearcoat is far gone on these old lights, the bare plastic has no UV protection at all.
The issue with these older polycarbonate lenses is not only do they turn dull and oxidize, since the factory applied clearcoat degrades over time, but they also develop stress cracks from old age and heat, and that cannot be fixed or corrected unfortunately. My LX is an 07 with very few miles, garaged in a northern climate all its life and even mine had a few of these stress cracks, as a few other older Toyota/Lexus vehicles in our family. I can only imagine what hotter climates do to these lenses. It’s a Toyota problem, not specific to the 100 Series.
Also, I believe Lou said he does not retrofit old headlights because during the baking process, the chrome inside the housings starts to delaminate. He only retrofits brand new headlights to avoid this happening, something to think about if you want to bake and open up your old lenses.
As for the high beams, Lou has a kit that basically replaces your halogen bulb in the high beam with a LED unit. Also with this kit installed, you can use the bi-xenon feature of the low beam projectors (someone correct me if I’m wrong on this one).
That’s all I got on the topic, I’m far from knowledgeable on this topic but those are the basics. I had Lou build me a new set of lights and his work is worth every penny!